This disclosure relates to network devices and network communication.
Wireless local area networks (WLANs) are increasingly being used in many different applications, e.g., in home entertainment and business applications.
In one application of a conventional WLAN, one or more wireless clients (e.g., telephone, speaker, television, projector, and so on) can be configured to be in communication with one or more wireless communication systems (e.g., a server, a network, a desktop workstation, laptop computer, and so on) to receive and transmit information.
WLANs generally specify the technologies for wireless communication. Example WLANs can be implemented according to one or more of the following standards: IEEE standards 802.11, 802.11a, 802.11b, 802.11g, 802.11n, 802.16 and 802.20. WLANs typically implement one or more communication protocols in which information is transmitted in packets. Such communication protocols can specify features such as packet size, packet content information, data rates, roaming, and so on. WLANs generally include a communication medium (or transmission channel) that is shared by transmitters (e.g., a wireless communication system and one or more wireless clients). To avoid collision between two transmitted packets on the shared communication medium, a WLAN can implement a CSMA/CA (carrier sense multiple access with collision avoidance) protocol.
FIG. 1 illustrates a timing sequence 100 for transmission of a packet according to a CSMA/CA protocol. When a wireless communication system wants to transmit a packet (e.g., to a wireless client), the wireless communication system first senses (or listens to) the shared communication medium to determine whether the shared communication medium is free (or idle). If the shared communication medium is sensed by the wireless communication system as being free, the wireless communication system waits for a DCF (Distributed Coordination Function) interframe space (DIFS), and then transmits a packet. Otherwise, the wireless communication system defers access to the shared communication medium until the shared communication medium is free, and the wireless communication system commences a backoff procedure. The backoff procedure reflects a delay of a number of random timing slots. The random delay occurs during a contention window so that the likelihood of collision between transmitted packets on the shared communication medium is reduced. Thereafter, the wireless communication system again senses the shared communication medium. If the shared communication medium is free, the wireless communication system transmits a next packet on the shared communication medium.
Within the CSMA/CA protocol, each wireless client is also operable to send an acknowledgement (ACK) packet each time the wireless client correctly receives a packet. ACK packets are typically sent after a short interframe space (SIFS) as shown in FIG. 1.
With respect to transmission of real-time data (e.g., streaming audio, video, and so on) in a conventional WLAN, a wireless communication system can send compressed real-time data through multicast network services to one or more wireless clients using standard protocols such as TCP/IP (Transmission Control Protocol/Internet Protocol) and RTP (Real-Time Transport Protocol). Although RTP provides end-to-end network transport functions suitable for transmission of real-time data in a WLAN, RTP typically does not provide QoS (Quality of Service)—e.g., RTP does not require that a wireless client return an ACK packet.